Spin valve sensor with a capping layer comprising cobalt

ABSTRACT

In one illustrative example of the invention, a spin valve sensor of a magnetic head has a sensor stack structure which includes a free layer structure and an antiparallel (AP) pinned layer structure separated by a spacer layer. A capping layer structure formed over the sensor stack structure includes a layer of cobalt (e.g. pure cobalt, oxidized cobalt, or cobalt-iron) as well as a layer of tantalum formed over it. Advantageously, the cobalt layer in the capping layer structure enhances the GMR and soft magnetic properties for thinner freelayer structures while maintaining a desirable slightly negative magnetostriction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to spin valve sensors of magneticheads, and more particularly to the use of cobalt in capping layers ofspin valve sensors.

2. Description of the Related Art

Computers often include auxiliary memory storage devices having media onwhich data can be written and from which data can be read for later use.A direct access storage device (disk drive) incorporating rotatingmagnetic disks are commonly used for storing data in magnetic form onthe disk surfaces. Data is recorded on concentric, radially spacedtracks on the disk surfaces. Magnetic heads including read sensors arethen used to read data from the tracks on the disk surfaces.

In high capacity disk drives, magnetoresistive read (MR) sensors,commonly referred to as MR heads, are the prevailing read sensorsbecause of their capability to read data from a surface of a disk atgreater linear densities than thin film inductive heads. An MR sensordetects a magnetic field through the change in the resistance of its MRsensing layer (also referred to as an “MR element”) as a function of thestrength and direction of the magnetic flux being sensed by the MRlayer.

The conventional MR sensor operates on the basis of the anisotropicmagnetoresistive (AMR) effect in which the MR element resistance variesas the square of the cosine of the angle between the magnetization ofthe MR element and the direction of sense current flow through the MRelement. Recorded data can be read from a magnetic medium because theexternal magnetic field from the recorded magnetic medium (the signalfield) causes a change in the direction of magnetization in the MRelement, which in turn causes a change in resistance in the MR elementand a corresponding change in the sensed current or voltage.

Another type of MR sensor is the giant magnetoresistance (GMR) sensormanifesting the GMR effect. In GMR sensors, the resistance of the MRsensing layer varies as a function of the spin-dependent transmission ofthe conduction electrons between magnetic layers separated by anon-magnetic layer (spacer) and the accompanying spin-dependentscattering which takes place at the interface of the magnetic andnon-magnetic layers and within the magnetic layers. GMR sensors usingonly two layers of ferromagnetic material (e.g., nickel-iron,cobalt-iron, or nickel-iron-cobalt) separated by a layer of nonmagneticmaterial (e.g., copper) are generally referred to as spin valve (SV)sensors manifesting the SV effect. In an SV sensor, one of theferromagnetic layers, referred to as the pinned layer, has itsmagnetization typically pinned by exchange coupling with anantiferromagnetic (AFM) layer (e.g., nickel-oxide, iron-manganese, orplatinum-manganese) layer. The pinning field generated by the AFM layershould be greater than demagnetizing fields to ensure that themagnetization direction of the pinned layer remains fixed duringapplication of external fields (e.g. fields from bits recorded on thedisk). The magnetization of the other ferromagnetic layer, referred toas the free layer, however, is not fixed and is free to rotate inresponse to the field from the information recorded on the magneticmedium (the signal field). A cap or capping layer of tantalum istypically formed over the sensor stack structure for protecting thesensor during and after its production.

There are several properties of a spin valve sensor which, if improved,will improve the performance of the magnetic head and increase the datastorage capacity of a disk drive. For example, it is generally desirableto increase the magnetoresistive coefficient Δr/R and decrease thecoercivity H_(c) of the free layer without substantially increasing thethickness of the sensor layers. An increase in the spin valve effect(Δr/R) equates to higher bit density (bits/square-inch of the rotatingmagnetic disk) read by read head. It is also desirable to keep themagnetostriction slightly negative or zero. If the free layers structurehas positive magnetostriction and is subjected to compressive stress,there will be a stress-induced anisotropy that urges the magnetic momentof the free layer from a position parallel to the ABS toward a positionperpendicular to the ABS. The result is undesirable read back asymmetryand instability. The compressive stress occurs after the magnetic headis lapped at the AMS to form the strip height of the sensor. Afterlapping, the free layer is in compression and this, in combination withpositive magnetostriction, causes the aforementioned read backasymmetry. If the free layer structure has negative magnetostriction incombination with compressive stress that the magnetic moment of the freelayer is actually strengthened along the position parallel to the ABS.Thus, it is desirable that the magnetostriction of the free layer bezero or only slightly negative.

Efforts continue to improve the properties of spin valve sensors. Whatare needed are ways in which to increase the magnetoresisitivecoefficient Δr/R, lower the coercivity H_(c), and substantiallyeliminate magnetostriction in a spin valve sensor.

SUMMARY

In one illustrative embodiment of the invention, a method of forming aread sensor of a magnetic head has a sensor stack structure whichincludes a free layer structure separated from an antiparallel (AP)pinned layer structure by a spacer layer. A capping layer structureformed over the sensor stack structure includes a layer of cobalt (e.g.pure cobalt, oxidized cobalt, or cobalt-iron) as well as a layer oftantalum formed over it. Preferably, the cobalt layer is oxidizedcobalt. Advantageously, the cobalt layer in the capping layer structureenhances the GMR and soft magnetic properties for thinner free layerstructures while maintaining a desirable slightly negativemagnetostriction.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings:

FIG. 1 is a plan view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2-2 of FIG. 1;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an air bearing surface (ABS) view of the magnetic head takenalong plane 5-5 of FIG. 2;

FIG. 6 is a partial view of the slider and a merged magnetic head asseen in plane 6-6 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7-7 of FIG.6 to show the read and write elements of the merged magnetic head;

FIG. 8 is a view taken along plane 8-8 of FIG. 6 with all material abovethe coil layer and leads removed;

FIG. 9 is an enlarged isometric illustration of a read head having aspin valve sensor;

FIG. 10 is an ABS illustration of a typical multi-layer structure of aspin valve sensor;

FIG. 11 is an ABS illustration of a first example of a multi-layerstructure of a spin valve sensor having cobalt formed in a cappinglayer;

FIG. 12 is an ABS illustration of a second example of a multi-layerstructure of a spin valve sensor having cobalt formed in the cappinglayer;

FIG. 13 is a flowchart which describes a method of making a spin valvesensor having cobalt formed in a capping layer;

FIG. 14 is an ABS illustration of a first example of a multi-layerstructure of a spin valve sensor with cobalt formed in a first AP pinnedlayer of an AP pinned layer structure;

FIG. 15 is an ABS illustration of a second example of a multi-layerstructure of a spin valve sensor with cobalt formed in a second APpinned layer of the AP pinned layer structure;

FIG. 16 is an ABS illustration of a third example of a multi-layerstructure of a spin valve sensor with cobalt formed in the first andsecond AP pinned layers of the AP pinned layer structure;

FIG. 17 is a graph which shows a magnetic moment as a function of anapplied field strength of a spin valve sensor having cobalt in its APpinned layer structure; and

FIG. 18 is a graph which shows a resistance as a function of an appliedfield strength of a spin valve sensor having cobalt in its AP pinnedlayer structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

Magnetic Disk Drive. Referring now to the drawings wherein likereference numerals designate like or similar parts throughout theseveral views, FIGS. 1-3 illustrate a magnetic disk drive 30. Disk drive30 includes a spindle 32 that supports and rotates a magnetic disk 34.Spindle 32 is rotated by a spindle motor 36 that is controlled by amotor controller 38. A slider 42 includes a combined read and writemagnetic head 40 and is supported by a suspension 44 and actuator arm 46that is rotatably positioned by an actuator 47. A plurality of disks,sliders, and suspensions may be employed in a large capacity directaccess storage device (DASD) as shown in FIG. 3. Suspension 44 andactuator arm 46 are moved by actuator 47 to position slider 42 so thatmagnetic head 40 is in a transducing relationship with a surface ofmagnetic disk 34. When disk 34 is rotated by spindle motor 36, slider 42is supported on a thin (typically, 0.05 μm) cushion of air (air bearing)between the surface of disk 34 and an air bearing surface (ABS) 48.Magnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of disk 34, as well as forreading information there from. Processing circuitry 50 exchangessignals, representing such information, with head 40, provides spindlemotor drive signals for rotating magnetic disk 34, and provides controlsignals to actuator 47 for moving slider 42 to various tracks. In FIG.4, slider 42 is shown mounted to a suspension 44. The componentsdescribed hereinabove may be mounted on a frame 54 of a housing 55, asshown in FIG. 3. FIG. 5 is an ABS view of slider 42 and magnetic head40. Slider 42 has a center rail 56 that supports magnetic head 40, andside rails 58 and 60. Rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of magnetic disk 34, cross rail 62 is at aleading edge 64 of slider 42 and magnetic head 40 is at a trailing edge66 of slider 42.

FIG. 6 is a side cross-sectional elevation view of a merged magnetichead 40, which includes a write head portion 70 and a read head portion72. Read head portion 72 includes a giant magnetoresistive (GMR) readhead which utilizes a spin valve sensor 74 of the present invention.FIG. 7 is an ABS view of FIG. 6. Spin valve sensor 74 is sandwichedbetween nonmagnetic electrically insulative first and second read gaplayers 76 and 78, and read gap layers 76 and 78 are sandwiched betweenferromagnetic first and second shield layers 80 and 82. In response toexternal magnetic fields, the resistance of spin valve sensor 74changes. A sense current I_(s) conducted through the sensor causes theseresistance changes to be manifested as potential changes. Thesepotential changes are then processed as read back signals by processingcircuitry 50 shown in FIG. 3.

Write head portion 70 of magnetic head 40 includes a coil layer 84sandwiched between first and second insulation layers 86 and 88. A thirdinsulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by coil layer84. The first, second and third insulation layers are referred to in theart as an “insulation stack”. Coil layer 84 and first, second and thirdinsulation layers 86, 88 and 90 are sandwiched between first and secondpole piece layers 92 and 94. First and second pole piece layers 92 and94 are magnetically coupled at a back gap 96 and have first and secondpole tips 98 and 100 which are separated by a write gap layer 102 at theABS. Since second shield layer 82 and first pole piece layer 92 are acommon layer, this head is known as a merged head. In a piggyback headan insulation layer is located between a second shield layer and a firstpole piece layer. As shown in FIGS. 2 and 4, first and second solderconnections 104 and 106 connect leads from spin valve sensor 74 to leads112 and 114 on suspension 44, and third and fourth solder connections116 and 118 connect leads 120 and 122 from the coil 84 (see FIG. 8) toleads 124 and 126 on suspension 44.

FIG. 9 is an enlarged isometric ABS illustration of read head 40 shownin FIG. 7 which includes spin valve sensor 74. First and second hardbias and lead layers 134 and 136 are connected to first and second sideedges 138 and 139 of spin valve sensor 74. This connection is known inthe art as a contiguous junction and is fully described in commonlyassigned U.S. Pat. No. 5,018,037 which is incorporated by referenceherein. First hard bias and lead layers 134 include a first hard biaslayer 140 and a first lead layer 142, and second hard bias and leadlayers 136 include a second hard bias layer 144 and a second lead layer146. Hard bias layers 140 and 144 cause magnetic fields to extendlongitudinally through spin valve sensor 74 for stabilizing the magneticdomains therein. Spin valve sensor 74 and first and second hard bias andlead layers 134 and 136 are located between the nonmagnetic electricallyinsulative first and second read gap layers 76 and 78. First and secondread gap layers 76 and 78 are, in turn, located between ferromagneticfirst and second shield layers 80 and 82.

FIG. 10 shows an ABS illustration of a typical multi-layered structureof a spin valve sensor 200 located between first and second read gaplayers 76 and 78. Spin valve sensor 200 includes a non-magneticelectrically conductive spacer (S) layer 202 which is located between anantiparallel (AP) pinned layer structure 204 and a free layer structure206. AP pinned layer structure 204 includes an antiparallel coupling(APC) layer 208 which is located between first and second ferromagneticAP pinned layers (AP1) and (AP2) 210 and 212. First AP pinned layer 210is exchange coupled to an antiferromagnetic (AFM) pinning layer 214which pins a magnetic moment 215 of first AP pinned layer 210perpendicular to the ABS in a direction out of or into sensor 200, asshown in FIG. 10. By strong antiparallel coupling between first andsecond AP pinned layers 210 and 212, a magnetic moment 216 of second APpinned layer 212 is antiparallel to magnetic moment 215. First, second,and third seed layers (SL1), (SL2) and (SL3) 218, 220, and 222 may beprovided between first read gap layer 76 and pinning layer 214 forpromoting a desirable texture of the layers deposited thereon. Freelayer structure 206 includes first and second free ferromagnetic layers(F1) and (F2) 224 and 226, with first free layer 224 interfacing spacerlayer 202. Free layer structure 224 has a magnetic moment 228 which isoriented parallel to the ABS and to the major planes of the layers in adirection from right to left, or from left to right, as shown in FIG.10. A cap or capping layer 234 is formed over free layer structure 206for protecting the sensor.

When a signal field from the rotating magnetic disk rotates magneticmoment 228 into the sensor, magnetic moments 228 and 216 become moreantiparallel which increases the resistance of the sensor to the sensecurrent (I_(S)). When a signal field rotates magnetic moment 228 of freelayer structure 206, magnetic moments 228 and 216 become more parallelwhich reduces the resistance of sensor 200 to the sense current (I_(S)).These resistance changes are processed as playback signals by processingcircuitry (i.e. processing circuitry 50 of FIG. 3).

The following materials may be utilized in the multilayered spin valvesensor 200 of FIG. 10. First, second, and third seed layers are made ofalumina (Al₂O₃), nickel-iron-chromium (NiFeCr), and nickel-iron (NiFe),respectively, from bottom to top; AFM layer 214 is made ofplatinum-manganese (PtMn) or alternatively of iridium-manganese (IrMn)or nickel-oxide (NiFe); AP pinned layers 210 and 212 are made ofcobalt-iron (CoFe); APC layer 208 is made of ruthenium (Ru); first andsecond free layers 224 and 226 are made of cobalt-iron (CoFe) andnickel-iron (NiFe), respectively; spacer layer 202 is made of copper(Cu); and capping layer 234 is made of tantalum (Ta). A copper (Cu)layer may be located on second free layer 226 for reflecting conductionelectrons back into the mean free path of conduction electrons.Thicknesses of particular materials may be 30 Angstroms of Al₂O₃ forfirst seed layer 218; 25 Angstroms of NiFeCr for second seed layer 220;10 Angstroms of NiFe for third seed layer 222; 150 Angstroms of PtMn forAFM layer 214, various thicknesses X of Co₉₀Fe₁₀ for first AP pinnedlayer 210; 8 Angstroms of Ru for APC layer 208; various thicknesses Z ofCo₉₀Fe₁₀ for second AP pinned layer 212; 20 Angstroms of Cu for spacerlayer 202; 15 Angstroms of Co₉₀ Fe₁₀ for first free layer 224; 15Angstroms of Ni₈₃Fe₁₇ for second free layer 226; and 40 Angstroms of Tafor capping layer 234.

Capping Layer Structure Which Includes A Cobalt Layer. FIG. 11 shows anABS illustration of a multi-layered structure of a spin valve sensor1100 of a magnetic head. Spin valve sensor 1100 is similar to that shownand described in relation to FIG. 10; however, a capping layer structure1102 of spin valve sensor 1100 has a layer 1104 which includes a cobalt(Co) alloy formed underneath a tantalum layer 1106. Specifically, layer1104 of spin valve sensor 1100 includes cobalt-iron (CoFe) orcobalt-iron-oxide (CoFeO). It has been discovered that, with use of thespecific materials in spin valve sensor 1100 as described, relativelythin layers of CoFe or CoFeO in capping layer structure 1102 enhances orincreases the Δr/R of spin valve sensor 1100. Preferably, the CoFe orCoFeO in capping layer structure 1102 may be formed to a thickness ofbetween about 3-6 Angstroms. Tantalum layer 1106 may be formed to athickness of between about 25-50 Angstroms. With use of capping layerstructure 1102, the Δr/R of spin valve sensor 1100 may be increasedbetween 2-4% given a fixed free layer thickness.

Although the CoFe or CoFeO in capping layer structure 1102 increasesspin valve sensor's 1100 Δr/R, the soft magnetic properties of spinvalve sensor 1100 degrade as a result. Specifically, the CoFe or CoFeOin capping layer structure 1102 makes the magnetostriction of free layerstructure 206 become near zero or positive when it is desirable for itto be slightly negative. CoFeO in capping layer structure 1102 alsocontributes to the moment of free layer structure 206, which makes itmore difficult to balance thickness, GMR, and magnetostriction of spinvalve sensor 200. However, since the use of CoFe or CoFeO in cappinglayer structure 1102 still has benefits (e.g. increased Δr/R), it may besuitable in some applications despite such concerns.

FIG. 12 shows an ABS illustration of another multi-layered structure ofa spin valve sensor 1200 of a magnetic head. Spin valve sensor 1200 isalso similar to that shown and described in relation to FIG. 10;however, a capping layer structure 1202 has a layer 1204 which includescobalt (Co) formed underneath a tantalum layer 1206. Specifically, layer1204 of spin valve sensor 1200 includes pure cobalt (Co) or oxidizedcobalt (CoO). Preferably, layer 1204 is oxidized cobalt. It has beendiscovered that with use of the specific materials in spin valve sensor1200 as described, relatively thin layers of Co or CoO in capping layerstructure 1202 enhances or increases the Δr/R of spin valve sensor 1200.Preferably, the Co or CoO in capping layer structure 1202 may be formedto a thickness of between about 2-6 Angstroms. Tantalum layer 1206 maybe formed to a thickness of between about 25-50 Angstroms. With use ofcapping layer structure 1202, the Δr/R of spin valve sensor 1200 may beincreased between 3-6% given a fixed free layer thickness.

Unlike capping layer structure 1102 of FIG. 11, the soft magneticproperties of spin valve sensor 1200 do not degrade as a result of usingthe cobalt in capping layer structure 1202. The magnetostriction of freelayer structure 1206 in FIG. 12 may be advantageously maintained in thedesirable slightly-negative range. Also advantageously, CoO in cappinglayer structure 1202 does not contribute in any significant way to themoment of freelayer structure 206. Using the capping layer structurewhich includes cobalt, the free layer structure may be made relativelythin (e.g. total magnetic thickness less than 20 Angstroms or between15-20 Angstroms) and/or the coercivity may be kept relatively low (e.g.less than 5 Oersteds or between 3-5 Oersteds).

Table 1 below provides measurement data for various properties of spinvalve sensors with and without cobalt in the cap layer structure. InTable 1, R_(s) is the resistance of the spin valve, Δr/R is themagnetoresistive coefficient, H_(c) is the coercivity of the free layer,H_(ch) is the hard-axis coercivity, H_(f) is the ferromagnetic couplingfield, and k is the magnetostriction coefficient. Columns 1-2 are datawith use of ion beam deposition (IBD) techniques for the AFM layer(PtMn), whereas columns 3-5 are data with use of physical vapordeposition (PVD) for the AFM layer. TABLE 1 Spin valve properties withand without CoO in the cap layer structure. Cap Layer With Without WithWith Composition Without CoO CoO (2 Å) CoO CoO (2 Å) CoO (2 Å) PtMnDeposition IBD IBD PVD PVD PVD AP layer 1 CoFe CoFe CoFe CoFe CoFeComposition AP layer 2 CoFe CoFe CoFe CoFe CoFe Composition Free LayerCoFe(14)/ CoFe(14.5)/ CoFe(14)/ CoFe(15)/ CoFe(9.5)/ CompositionNiFe(14) NiFe(14.5) NiFe(14) NiFe(14.5) NiFe(9) Free Layer 28 29 28 29.518.5 Thickness (Å) Δr/R (%) 12.42 13.2 12.93 13.17 11.5 R_(s) (Ω/sq.) 2423.6 24 23.8 26.5 H_(c) (Oe) 4.2 4.4 4.8 4.5 4.2 H_(ch) (Oe) 0.7 0.6 0.80.58 1 H_(f) (Oe) −17 −17.6 −19 −8 −21 λ (×10⁻⁶) −0.43 −0.71 −0.84 −1.29−1.29As apparent from the Table 1 data, the Δr/R of a spin valve sensorhaving a CoO cap increases about 6%. The H_(c) and H_(ch) provided by an18.5 Å thick free layer using the 2 Å CoO cap are as good as thoseprovided by a 30 Å thick free layer without the CoO cap. Also, the CoOin the capping layer structure does not make the magnetostriction of thefree layer positive.

Table 2 below provides additional measurement data for variousproperties of spin valve sensor 1200 of FIG. 12 where the thickness ofCoO in cap layer structure 1202 is widely varied. In Table 2, R_(s) isthe resistance of the spin valve, Δr/R is the magnetoresistivecoefficient, H_(e) is the ferromagnetic coupling field, H_(ce) is theeasy-axis coercivity, H_(ch) is the hard-axis coercivity, and λ is thefree layer magnetostriction coefficient. TABLE 2 Sensor propertiesvarying the thickness of CoO in the cap layer structure. CoO CapFreelayer Thickness R_(s) Δr/R H_(e) H_(ce) H_(ch) Thickness λ (Å)(Ω/sq.) (%) (Oe) (Oe) (Oe) (Å) (×10⁻⁶) 3 23.6 13.2 −17.6 4.4 0.6 29.1−0.71 4 23.9 12.7 −12.5 4.2 0.6 29.7 −0.58 5 23.9 12.6 −12.1 3.6 0.730.0 −0.62 6 24.0 12.9 −11.5 4.7 0.7 29.4 −0.59As apparent from Table 2, the properties of the spin valve structure aresuitable even for a relatively thick layer of CoO (e.g. 6 Å) in the caplayer structure. Also, the cobalt film oxidizes and does not contributeto the freelayer moment even when the cobalt thickness is widely varied.

FIG. 13 is a flowchart which describes a method of making a spin valvesensor of the type described in relation to FIGS. 11-12. Although themethod described in relation to the flowchart of FIG. 13 relates to abottom-pinned type spin valve, one skilled in the art will understandthat it is applicable to top-pinned type spin valve as well as others.

Beginning at a start block 1300, a seed layer is deposited over asubstrate (step 1302), such as over a dielectric gap layer of a magnetichead. In the present embodiment, the seed layer is a tri-layer seedlayer of Al₂O₃, NiFeCr, and NiFe, from bottom to top. Next, anantiferromagnetic (AFM) layer (e.g. PtMn) is deposited over the seedlayer (step 1304). An antiparallel (AP) pinned layer structure is thenformed over the AFM layer (step 1306). The AP pinned layer structureincludes first and second AP pinned layers (e.g. CoFe) which areseparated by an antiparallel coupling (APC) layer (e.g. Ru). Next, afree layer structure is formed over the AP pinned layer structure (step1308). The free layer structure may be a multi-layer structure, such asbilayer structure of CoFe and NiFe (separated from the AP pinned layerstructure by a non-magnetic electrically conductive spacer layer). Inthe present application, all of these deposited layers including the AFMlater, the AP pinned layer structure, and the free layer structure, maybe referred to as a sensor stack structure.

In steps 1310-1314, a capping layer structure is formed over the sensorstack structure. In particular, cobalt is deposited in oxygen atmosphereover the free layer structure (step 1310). The cobalt may be depositedto a thickness of between about 2-6 Angstroms, for example. The partialpressure of the oxygen may be about 10⁻⁵ Torrs, for example. Next, thecobalt is subjected to a natural oxidation process (step 1312). Thisoxidation process may be performed for duration of between about 10-300seconds and, in this particular embodiment, about 30 seconds. Next, alayer of tantalum is deposited over the oxidized cobalt. The tantalummay be deposited to a thickness of between about 25-50 Angstroms. Theflowchart ends at an end block 1316, where subsequent processing stepsto complete the manufacture of the magnetic head using conventional orother processes may be utilized. The result is a spin valve sensor ofthe type described in relation to FIG. 12, for example.

As described, a spin valve sensor of the present invention has a sensorstack structure which includes a free layer structure and anantiparallel (AP) pinned layer structure which are separated by anon-magnetic electrically conductive spacer layer. A capping layerstructure formed over the sensor stack structure includes a layer ofcobalt (e.g. pure cobalt, oxidized cobalt, or cobalt-iron) as well as alayer of tantalum formed over it. Preferably, the cobalt is oxidized.Advantageously, the cobalt layer in the capping layer structure enhancesthe GMR and soft magnetic properties for thinner freelayer structures. Amethod of forming the spin valve sensor includes the acts of forming asensor stack structure which includes a free layer structure and anantiparallel (AP) pinned layer structure separated by a spacer layer;and forming, over the sensor stack structure, a capping layer structurewhich includes a cobalt layer.

A disk drive of the present invention may include a housing; a magneticdisk rotatably supported in the housing; a magnetic head assembly; asupport mounted in the housing for supporting the magnetic head assemblyso as to be in a transducing relationship with the magnetic disk; aspindle motor for rotating the magnetic disk; an actuator positioningmeans connected to the support for moving the magnetic head assembly tomultiple positions with respect to said magnetic disk; a processorconnected to the magnetic head assembly, to the spindle motor, and tothe actuator for exchanging signals with the magnetic head assembly forcontrolling movement of the magnetic disk and for controlling theposition of the magnetic head assembly; the magnetic head assemblyincluding a read head; the read head including a spin valve sensorhaving a sensor stack structure which includes a free layer structureand an antiparallel (AP) pinned layer structure which are separated by aspacer layer; a capping layer structure formed over the sensor stackstructure; wherein the capping layer structure comprises a cobalt layer.

Antiparallel (AP) Pinned Layer Structure Comprising A Cobalt Layer.FIGS. 14-16 show ABS illustrations of multi-layered structures of spinvalve sensors 1400, 1500, 1600. Spin valve sensors 1400, 1500, and 1600of FIGS. 14-16 are similar to that shown and described in relation toFIG. 10; however, at least one of the antiparallel (AP) pinned layers inthe AP pinned layer structures includes cobalt (Co) in place of thecobalt-iron (CoFe) alloy. Preferably, the cobalt in the AP pinnedlayer(s) is pure cobalt without any iron content.

Spin valve sensor 1400 of FIG. 14 includes cobalt in a second AP pinnedlayer 1402 of an AP pinned layer structure 1404 but still utilizescobalt-iron in first AP pinned layer 210. On the other hand, spin valvesensor 1500 of FIG. 15 includes cobalt in a first AP pinned layer 1502of an AP pinned layer structure 1504 but still utilizes cobalt-iron insecond AP pinned layer 212. Finally, spin valve sensor 1600 of FIG. 16includes cobalt in both first and second AP pinned layers 1602 and 1604of an AP pinned layer structure 1604. Note that, in each of theembodiments of FIGS. 14-16, cobalt-iron (not pure cobalt) andnickel-iron are utilized in free layer structure 206. Advantageously,the use of cobalt in at least one of the AP pinned layers increases themagnetoresistive coefficient Δr/R of the sensor.

Table 3 below provides measurement data for properties of various spinvalve sensors where cobalt is utilized in the AP pinned layer structure(e.g. spin valve sensors 1400, 1500, and 1600 of FIGS. 14-16). In Table3, R_(s) is the resistance of the spin valve, Δr/R is the magneticcoefficient, H_(c) is the coercivity of the free layer, H_(ch) is thehard-axis coercivity, H_(f) is the ferromagnetic coupling field, and λis the magnetostriction coefficient. TABLE 3 Sensor properties with andwithout cobalt in the AP pinned layer structure. AFM Layer CompositionPtMn PtMn PtMn & Thickness (Å) 150 150 150 AP Layer 1 Co CoFe CoFeComposition AP Layer 2 Co Co CoFe Composition Free Layer CoFe/ CoFe/CoFe/ Composition NiFe NiFe NiFe Free Layer 29 29 28 Thickness (Å)Δr/R(%) 13.4 13.8 12.42 R_(s)(Ω/sq.) 22.5 22.5 24 H_(c)(Oe) 8.68 4.8 4.2H_(ch)(Oe) 0.8 0.7 0.7 H_(f)(Oe) −17 −21 −17 λ(×10⁻⁶) −.08 −0.71 −0.43

As apparent, the use of cobalt in at least one of the AP pinned layerstructures of a spin valve sensor enhances or increases the Δr/R.Preferably, cobalt is utilized in only one of the AP pinned layers andcobalt-iron is utilized in the other AP pinned layer, as provided inFIG. 3 and the Table 3 data. With use of cobalt in the AP pinned layerstructure, the Δr/R of spin valve sensor 1100 may be increased between5-10% from spin valve sensor 200 of FIG. 10. Preferably, the thicknessof Co varies between 10-30 Angstroms. Other properties of the spin valvesensor, such as its magnetostriction, remain suitable for theapplication. Note that, since the use of cobalt in the free layerstructure results in relatively larger coercivity, cobalt-iron (notcobalt) is utilized in the free layer structure.

To construct a spin valve sensor of FIGS. 14-16, a sensor stack isformed which includes a free layer structure and an AP pinned layerstructure separated by a non-magnetic electrically conductive spacerlayer. The AP pinned layer structure is formed with a first AP pinnedlayer, a second AP pinned layer, and an APC layer between the first andsecond AP pinned layer. At least one of the first and the second APpinned layers consists of cobalt and, preferably, only one of the APpinned layers consists of cobalt and the other AP pinned layer comprisescobalt-iron. The layers are formed with the use of conventionaldeposition and etching techniques.

FIG. 17 is a graph 1700 which shows the magnetic moment as a function ofapplied field strength of a spin valve sensor having cobalt in the APpinned layer structure. In FIG. 18, a graph 1800 which shows theresistance as a function of applied field strength of a spin valvesensor having cobalt in the AP pinned layer structure is shown. Bothgraphs 1700 and 1800 of FIGS. 17 and 18 relate to a spin valve sensorhaving the cobalt in only a single AP pinned layer (the second AP pinnedlayer) where the AFM layer is platinum-manganese.

As described, a spin valve sensor (which may be a bottom-pinned type ortop-pinned type) includes a free layer structure; an antiparallel (AP)pinned layer structure; and a non-magnetic electrically conductivespacer layer in between the free layer structure and the AP pinned layerstructure. The AP pinned layer structure includes a first AP pinnedlayer; a second AP pinned layer; and an antiparallel coupling (APC)layer formed between the first and the second AP pinned layer. One ofthe first and the second AP pinned layers consist of cobalt and theother one includes cobalt-iron. The pure cobalt may be provided in thefirst AP pinned layer, the second AP pinned layer, or in both layers.The use of the cobalt in one of the AP pinned layers increases the Δr/Rof the spin valve sensor. Preferably, the use of the cobalt results in aΔr/R of the spin valve sensor being greater than 12% and a coercivityH_(c) being less than 5 Oersteds. In a method to construct such a spinvalve sensor, a stack structure is formed which includes a free layerstructure and an antiparallel (AP) pinned layer structure separated by anon-magnetic electrically conductive spacer layer. The AP pinned layerstructure is formed with a first AP pinned layer, a second AP pinnedlayer, and an antiparallel coupling (APC) layer between the first andthe second AP pinned layers, wherein one of the AP pinned layersconsists of cobalt and the other one includes cobalt-iron. The layersmay be formed using conventional deposition and etching techniques.

A disk drive of the present invention includes a housing; a magneticdisk rotatably supported in the housing; a magnetic head assembly; asupport mounted in the housing for supporting the magnetic head assemblyso as to be in a transducing relationship with the magnetic disk; aspindle motor for rotating the magnetic disk; an actuator positioningmeans connected to the support for moving the magnetic head assembly tomultiple positions with respect to said magnetic disk; and a processorconnected to the magnetic head assembly, to the spindle motor, and tothe actuator for exchanging signals with the magnetic head assembly forcontrolling movement of the magnetic disk and for controlling theposition of the magnetic head assembly. The magnetic head assemblyincludes a read head having a spin valve sensor which includes anantiparallel (AP) pinned layer structure and the AP pinned layerstructure. The AP pinned layer structure includes a first AP pinnedlayer; a second AP pinned layer; an antiparallel coupling (APC) layerformed between the first and the second AP pinned layer; wherein one ofthe AP pinned layers consists of cobalt and the other includescobalt-iron.

It is to be understood that the above is merely a description ofpreferred embodiments of the invention and that various changes,alterations, and variations may be made without departing from the truespirit and scope of the invention as set for in the appended claims.Although the specific sensors described herein have been bottom-pinnedtype spin valves, one skilled in the art will understand that it isapplicable to top-pinned type spin valves and others. Few if any of theterms or phrases in the specification and claims have been given anyspecial meaning different from their plain language meaning, andtherefore the specification is not to be used to define terms in anunduly narrow sense.

1. A spin valve sensor, comprising: a sensor stack structure whichincludes: a free layer structure; an antiparallel (AP) pinned layerstructure; a non-magnetic electrically conductive spacer layer inbetween the free layer structure and the AP pinned layer structure; acapping layer structure formed over the sensor stack structure; and thecapping layer structure comprising a cobalt layer.
 2. The spin valvesensor of claim 1, wherein the cobalt layer comprises pure cobalt. 3.The spin valve sensor of claim 1, wherein the cobalt layer comprisesoxidized cobalt.
 4. The spin valve sensor of claim 1, wherein the cobaltlayer comprises a cobalt alloy.
 5. The spin valve sensor of claim 1,wherein the capping layer structure further comprises a tantalum layerformed over the cobalt layer.
 6. The spin valve sensor of claim 1,further comprising: wherein the cobalt layer comprises one of purecobalt and oxidized cobalt; and wherein the capping layer structurefurther comprises a tantalum layer formed over the cobalt layer.
 7. Thespin valve sensor of claim 1, wherein the free layer structure includesat least one of cobalt-iron and nickel iron.
 8. The spin valve sensor ofclaim 1, wherein the AP pinned layer structure comprises cobalt orcobalt alloy.
 9. The spin valve sensor of claim 1, wherein the freelayer is formed between the capping layer structure and the AP pinnedlayer structure.
 10. The spin valve sensor of claim 1, wherein the APpinned layer structure is formed between the capping layer structure andthe free layer structure.
 11. The spin valve sensor of claim 1, whereinthe AP pinned layer structure comprises: a pinned layer; a referencelayer; and an antiparallel coupling layer between the pinned layer andthe reference layer.
 12. The spin valve sensor of claim 1, wherein acoercivity H_(c) of the spin valve sensor is less than 5 Oersteds. 13.The spin valve sensor of claim 1, wherein a magnetostriction of the spinvalve sensor is negative.
 14. A disk drive, comprising: a housing; amagnetic disk rotatably supported in the housing; a magnetic headassembly; a support mounted in the housing for supporting the magnetichead assembly so as to be in a transducing relationship with themagnetic disk; a spindle motor for rotating the magnetic disk; anactuator positioning means connected to the support for moving themagnetic head assembly to multiple positions with respect to saidmagnetic disk; a processor connected to the magnetic head assembly, tothe spindle motor, and to the actuator for exchanging signals with themagnetic head assembly for controlling movement of the magnetic disk andfor controlling the position of the magnetic head assembly; the magnetichead assembly including a read head; the read head including a spinvalve sensor; the spin valve sensor comprising: a sensor stack structurewhich includes: a free layer structure; an antiparallel (AP) pinnedlayer structure; a non-magnetic electrically conductive spacer layer inbetween the free layer structure and the AP pinned layer structure; acapping layer structure formed over the sensor stack structure; and thecapping layer structure comprising a cobalt layer.
 15. The disk drive ofclaim 14, wherein the cobalt layer comprises pure cobalt.
 16. The diskdrive of claim 14, wherein the cobalt layer comprises oxidized cobalt.17. The disk drive of claim 14, wherein the cobalt layer comprisescobalt-iron.
 18. The disk drive of claim 14, wherein the capping layerstructure further comprises a tantalum layer formed over the cobaltlayer.
 19. The disk drive of claim 14, further comprising: wherein thecobalt layer comprises one of pure cobalt and oxidized cobalt; andwherein the capping layer structure further comprises a tantalum layerformed over the cobalt layer.
 20. The disk drive of claim 14, whereinthe free layer structure is formed between the capping layer structureand the AP pinned layer structure.
 21. The disk drive of claim 14,wherein the AP pinned layer structure is formed between the cappinglayer structure and the free layer structure.
 22. The disk drive ofclaim 14, wherein a coercivity H_(c) of the spin valve sensor is lessthan 5 Oersteds.
 23. The disk drive of claim 14, wherein amagnetostriction of the spin valve sensor is negative.
 24. A method offorming a spin valve sensor for magnetic head, comprising: forming asensor stack which includes a free layer structure and an antiparallel(AP) pinned layer structure which are separated by a non-magneticelectrically conductive spacer layer, and forming, over the sensor stackstructure, a capping layer structure which includes a cobalt layer. 25.The method of claim 24, wherein the cobalt layer comprises pure cobalt.26. The method of claim 24, wherein the cobalt layer comprises oxidizedcobalt.
 27. The method of claim 24, wherein the act of forming thecapping layer structure comprises the further act of: oxidizing thecobalt layer.
 28. The method of claim 24, wherein the cobalt layercomprises cobalt-iron.
 29. The method of claim 24, wherein the act offorming the capping layer structure comprises the further act of:forming a tantalum layer over the cobalt layer.
 30. The method of claim24, wherein the act of forming the capping layer structure comprisesfurther acts of: oxidizing the cobalt layer; and forming a tantalumlayer over the oxidized cobalt layer.